Influence of coherent intermetallic nano-precipitates on the nano-level mechanical and tribological properties of the Laser-Powder bed fused Scalmalloy

Scalmalloy alloys fabricated by Laser-Powder Bed Fusion (L-PBF) process are extensively used in the field of aerospace, construction, and automotive applications due to its lightweight, corrosion resistant qualities and fine microstructure. But, there was a lack of in-depth study in the nano-level mechanical properties of the Scalmalloy. So, the prime novelty of this research work is to examine the nano-level mechanical behavior with respect to nano-level precipitations due to Sc-Zr addition. In this work, the L-PBFed Scalmalloy was examined for the irregularities and the grain distributions using Optical Microscopy (OM) and Field Emission Scanning Electron Microscopy (FE-SEM) with Energy-Dispersive X-ray spectroscopy (EDX) analysis. The formation of Al₃Sc precipitates was identified using X-ray diffraction (XRD) and Transmission Electron microscopy (TEM) analysis. Further, the influence of precipitates on the grain orientation was evaluated through Electron Backscatter Diffraction (EBSD) analysis. The nano-hardness and nano-wear testing was performed on the L-PBFed Scalmalloy. The maximum nano-hardness and reduced modulus of 2.19 GPa and 87.50 GPa was obtained from the average of 400 indentations. The nano-hardness mapping and reduced modulus mapping proved the homogenous dispersion of the precipitation. From the topographic wear tracks in the nano-wear analysis, the average worn-out height of 250.89 nm was observed and the fluctuation in the co-efficient of friction (CoF) confirms the formation of ceramic phase Al₃Sc precipitates which resists the worn-out height. Tensile strength of the L-PBFed Scalmalloy was evaluated based on the 3 strain rates (3.3 × 10⁻⁵, 1.6 × 10⁻⁵ and 2 × 10⁻⁴ s⁻¹) and the outcome shows that the Scalmalloy exhibits negative strain rate and serration caused by Portevin-Le Chatelier effect on the Al₃Sc precipitates and the Mg content.